JPH101568A - Polyolefin composition and food packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition which can give moldings which scarcely emit unpleasant odors when heated, have excellent resistance to thermal discoloration and are suited for food packaging containers by mixing a polyolefin with an inorganic filler, a specified adsorbent inorganic substance, a specified antioxidant and a lubricant. SOLUTION: This composition is prepared by mixing 100 pts.wt. polyolefin with 10-150 pts.wt. inorganic filler, 0.5-12 pts.wt. at least one adsorbent inorganic substance selected from the group consisting of zeolites, fraipontite/silica composite materials and hydrotalcite, 0.05-3 pts.wt. phenolic antioxidant and 0.05-3 pts.wt. fatty acid amide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin composition comprising a polyolefin such as polyethylene and polypropylene mixed with a large amount of an inorganic filler, and more particularly to a food packaging container which hardly generates an unpleasant odor even when heated. It relates to a suitable polyolefin-based composition.

[0002]

2. Description of the Related Art Polyolefins such as polyethylene and polypropylene are widely used as general living materials and industrial materials. Polyolefin-based compositions are often mixed with a large amount of inorganic filler in order to prevent the molded article from being discarded and incinerated, generating high heat and damaging the incinerator. In addition, various compounding agents such as a lubricant and an antioxidant are mixed for practical use in order to improve workability and prevent deterioration during heat molding. However, polyolefin molded products containing a large amount of inorganic fillers have been significantly prevented from thermal degradation by the addition of phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, etc. In addition, a strong unpleasant odor and an odor of the inorganic filler itself, which are considered to be caused by the catalytic action of the inorganic substance and the decomposition reaction product of the antioxidant, were generated, thereby causing a problem of deteriorating the working environment of the molding and processing of the polyolefin composition. . Polyolefins are used in large quantities, especially for food packaging, because trays and boxes can be mass-produced at low cost and are clean. However, with the widespread use of microwave ovens, food containers are often heated prior to meals, and it has become desirable to minimize the generation of unpleasant odors from the viewpoint of using molded articles. Various methods for suppressing the generation of unpleasant odors have been studied so far. A method in which an inorganic filler is neutralized with a base to increase the solid acid strength value and used (JP-A-51-145554).
No.) was proposed, but the pretreatment step of the inorganic filler was so extensive that it was not industrially effective. Also, a method of adding distearyl pentaerythritol diphosphite (Japanese Patent Application Laid-Open No. 50-139636) and a method of adding a fatty acid metal salt or a fatty acid amide (Japanese Patent Application Laid-Open No. 53-142455).
), A method of adding a cinnamic acid alkyl ester derivative and a dialkylthiodiacetate (Japanese Patent Application Laid-Open No. 52-1464).
No. 6), a method of adding a alkane sulfonate having 12 to 20 carbon atoms and a nitrogen compound such as melamine (JP-A-55-45).
No. 733) has been proposed, but none of them has been sufficiently deodorized. In addition, in the polyolefin-based composition, in preventing the color tone from being impaired,
It is still demanded that thermal discoloration is difficult during molding.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to obtain a polyolefin composition which gives a molded article having less unpleasant odor under heating and excellent heat discoloration resistance. 1 selected from the group consisting of, frypontite-silica composite and hydrotalcite
The present inventors have found that the above objects can be achieved by blending a specific amount of at least one or more kinds of adsorptive inorganic substances with a fatty acid amide and a phenolic antioxidant, and have completed the present invention based on this finding.

[0004]

According to the present invention, (1) 100 parts by weight of (A) a polyolefin, (B) 10 to 150 parts by weight of an inorganic filler, and (C) zeolite, frypontite-silica A polyolefin-based composition comprising at least one adsorbent inorganic substance selected from the group consisting of a composite and hydrotalcite; (2) (A) 100 parts by weight of a polyolefin, (B) an inorganic filler 10 to 150 parts by weight, (C) one or more adsorbable inorganic substances selected from the group consisting of zeolite, frypontite-silica composite and hydrotalcite
12 parts by weight, (D) phenolic antioxidant 0.05 to
3 parts by weight and (E) 0.05 to 3.0 parts by weight of a fatty acid amide, and a polyolefin-based composition, and (3) a composition according to the above (1) or (2). Provided is a food packaging container.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyolefin used as the component (A) in the present invention is a homopolymer of α-olefin such as ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, or a random or block copolymer. High-density polyethylene (HDPE), low-density polyethylene (LDPE), polybutene-1, polyisobutene, poly-3-methyl-butene-1, poly-4-methyl-pentene-1, ethylene-propylene copolymer,
Ethylene-butene-1 copolymer, propylene-4-methyl-pentene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer,
Decene-1-methyl-pentene-1 copolymer and the like are used, and these are used alone or in combination.
Particularly, HDPE and an ethylene-propylene block copolymer are preferred.

Inorganic fillers used as component (B) in the present invention include silicate compounds such as talc, mica, kaolin and silica sand; metal oxides such as alumina, titanium oxide and magnesium oxide; calcium carbonate and the like. Carbonates; sulfates such as calcium sulfate and barium sulfate; and hydroxides such as calcium hydroxide and aluminum hydroxide. Particularly, talc, mica or silica is preferred. The inorganic filler of the component (B) of the present invention does not include an adsorbable inorganic substance of the component (D) described later. The amount of the inorganic filler in the present invention is 10 to 150 parts by weight, preferably 20 to 130 parts by weight, per 100 parts by weight of the polyolefin (A). If the compounding amount of the inorganic filler is less than 10 parts by weight, the effect of reducing the calorific value of the molded article during combustion is small, and the rigidity and heat resistance of the molded article are deteriorated. On the other hand, even if it is blended in a large amount exceeding 150 parts by weight,
The processability, moldability, etc., deteriorate, and the mechanical strength, such as the impact resistance, of the molded product deteriorates.

In the present invention, at least one adsorbable inorganic substance selected from the group consisting of zeolite, fryponite-silica composite and hydrotalcite is used as the component (C). The zeolite is M _{x / n} · [(AlO
₂ ) A natural or synthetic inorganic substance represented by _x · (SiO ₂ ) _y ] · ZH ₂ O. Here, M is a metal ion having a valence of n, and x and y are tetrahedral numbers per single lattice.
As long as x / y is 1.1 or less, x is 4 to 4 in nature.
8, a value of 12 to 86 in synthesis, and y is 8 to 4 in nature.
0, a value of 12 to 136 is often used in the synthesis. Z is an integer of 13 to 27 in nature and 4.5 to 264 in synthesis. Typical examples are naturally occurring mondenite, Na
₂ O.Al ₂ O ₃ .10SiO ₂ .6H ₂ O. For synthesis, Mizucalizer DS manufactured by Mizusawa Chemical Co., Ltd., Na ₂ O.Al ₂
O ₃ · 2SiO ₂ · 4.5H ₂ O and the like. Zeolite is an inorganic substance having an adsorption performance having a polyhedral crystal structure.

[0008] The frypontite-silica composite is (Z
n ₆ -nAl _n ) (Si ₄ -nAl _n ) O ₁₀ (OH) ₈
A unit layer of fine crystals of frypontite of aluminosilicate metal salt mainly composed of zinc salt represented by a chemical formula of nH ₂ O is supported around silica particles.
A typical example is 5ZnO.Al ₂ O ₃ .3-4SiO
Mizukanite HP manufactured by Mizusawa Chemical Co., Ltd. in which ₂ is supported on amorphous silica. This frypontite is an inorganic substance having adsorption performance on both the front and back surfaces of the unit layer.

Hydrotalcite has the general formula [Mg _1-x
Al _x (OH) ₂ ] ^{x +} [(CO ₃ ) _{x / 2} · mH ₂ O] ^x-
Is an inorganic substance having an adsorption performance, having a layered crystal structure composed of a positively charged basic layer and a negatively charged intermediate layer represented by Where x is greater than 0 and 0.3
It is a number of 3 or less. In nature, Mg ₆ Al ₂ (OH) ₁₆
CO ₃ .4H ₂ O (x = 0.25, m = 4)
In the synthesis, Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂
Those having O (x = 0.3, m = 3.5) are exemplified as commercial products.

The amount of at least one adsorbent inorganic substance selected from the group consisting of zeolite, component (F), frypontite-silica composite and hydrotalcite used as component (C) in the present invention is as follows: Polyolefin 1
0.5 to 12 parts by weight, more preferably 2 to 10 parts by weight, and even more preferably 2.5 to 12 parts by weight, per 100 parts by weight.
8 parts by weight. When the amount of the adsorptive inorganic substance is less than 2.0 parts by weight, there is no effect of reducing the unpleasant odor, and when the amount of the adsorptive inorganic substance is more than 10 parts by weight, the composition becomes hygroscopic. The molded article tends to foam due to heat during molding. In the present invention, the component (C) has a function of adsorbing an odor and an effect of preventing thermal discoloration of a polyolefin molded article under heating.

The polyolefin composition of the present invention usually further comprises a phenolic antioxidant, a phosphorus antioxidant,
An antioxidant such as a sulfur-based antioxidant is blended. Phenolic antioxidants include n-octadecyl-3-
(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate, tetrakis [methylene-
3- (3 ', 5'-ditert-butyl-4'-hydroxyphenyl) propionate] methane, 2,4,5
-Trihydroxybutyrophenone, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-α
-Dimethylamino-p-cresol, 4,4'-bis (2,6-ditert-butylphenol), 2,2
Derivatives of '-methylene-bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl-6-tert-butylphenol), 6-tert-butyl-3-methylphenol, 1,
3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), bis (3 -Methyl-4-
(Hydroxy-5-tert-butylpentyl) sulfide, dialkylphenol sulfide and the like.

As the phosphorus antioxidants, distearyl pentaerythritol diphosphite, bis (2,4-
(Ditertiary butylphenyl) pentaerythritol diphosphite, tris (2,4-ditertiarybutylphenyl) phosphite, tetrakis (2,4-ditertiarybutylphenyl) 4,4′-biphenyldiphosphite, trinonylphenylphosphite Fight and the like. As the sulfur-based antioxidant, distearyl thiodipropionate, dilauryl thiodipropionate and the like can be used. As the antioxidant blended in the polyolefin composition of the present invention, a phenolic antioxidant is particularly preferable, and among them, n-octadecyl-3- (3
', 5'-Ditert-butyl-4'-hydroxyphenyl) propionate is preferred. The compounding amount of the antioxidant compounded in the polyolefin composition of the present invention is:
0.0 parts per 100 parts by weight of the polyolefin (A)
Preferably 5 to 3 parts by weight, more preferably 0.1 to 2.0 parts by weight. If the amount of the antioxidant is less than 0.05 part by weight, the antioxidant effect tends to be small, and if the amount is more than 3 parts by weight, adverse effects are likely to occur in terms of odor.

[0013] A lubricant is usually added to the polyolefin composition of the present invention. Examples of such lubricants include primary and secondary amides of saturated and unsaturated fatty acids such as lauric amide, palmitic amide, stearic amide, oleic amide, and behenic amide, and amides in one molecule such as ethylenebisstearic amide. Fatty acid amides such as bisamides containing two bonds; higher fatty acids having 8 to 22 carbon atoms; metal salts of the same fatty acids such as aluminum, calcium, magnesium, zinc and lithium; tributyl acetylcitrate and di-2-ethylhexyl adipate Fatty acid esters of monohydric or polyhydric alcohols such as ethanediol montanic acid ester, poly (1,3-butanediol-adipate) ester, methyl acetyl ricinoleate, poly (propylene glycol-adipate laurate) ester; triglyceride; Dimethyl polysilo Silicone oils such as sun, methylphenylpolysiloxane and polyoxyalkylene-dimethylpolysiloxane; rosin and rosin derivatives; aliphatic hydrocarbons such as liquid paraffin, synthetic paraffin, petroleum wax, montan wax, and hydrogenated polybutene; .

The preferred lubricant in the present invention is a fatty acid amide, particularly preferably ethylene bisstearic acid amide. The amount of the lubricant is preferably 0.05 to 3.0 parts by weight, more preferably 0.15 to 1.5 parts by weight, per 100 parts by weight of the component (A) polyolefin. If the compounding amount of the lubricant is less than 0.05 part by weight, the lubricity tends to be insufficient at the time of molding, the surface of the molded article is roughened, and the stability of processing is easily hindered. On the other hand, if it is more than 3.0 parts by weight, the lubricity tends to be excessive during molding, and the dispersibility of the component (B) inorganic filler tends to deteriorate. Further, the processing stability tends to deteriorate.

[0015] In addition to the above components, the composition of the present invention comprises
An antistatic agent, a foaming agent, a pigment and the like may be added within a range that does not impair the effects of the present invention. The composition of the present invention
It is preferable that the above components are in a state of being uniformly mixed. Usually, the above components are stirred with a Henschel mixer or the like,
After mixing, a sheet was obtained at 180 to 250 ° C. using an extruder or a roll, and the sheet was passed through a sheet pelletizer.
First, pellets having a diameter of 2 to 4 mm and a length of 3 to 5 mm are formed. In order to obtain a molded product such as a food packaging container using the pellets, usually, a sheet is molded at a temperature of 180 to 250 ° C. with a T-die extruder or a calender roll,
The sheet is subjected to a vacuum forming machine or a vacuum press forming machine to form a packaging container. Further, a method of forming a packaging container by using the pellets in a blow molding machine or an injection molding machine can also be adopted.

[0016]

Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The parts and percentages are by weight unless otherwise specified. Tests and evaluations were as follows. (1) Preparation of pellets The compounding agent was mixed at 140 ° C with a 75-liter Henschel mixer manufactured by Mitsui Miike Kakoki Co., Ltd., and then 180-220 ° C with a twin screw extruder TEM35B manufactured by Toshiba Machine Co., Ltd.
At a temperature of 5 ° C. to obtain pellets with a die having a diameter of 3 mm. (2) Preparation of sheet Using the pellet obtained in the above (1), using a single screw vent type extruder PM-65 manufactured by Mitsubishi Heavy Industries, Ltd., a width of 5 mm.
The sheet is extruded with a 00 mm T die to obtain a sheet having a thickness of 0.65 mm. (3) Preparation of tray Using the sheet obtained in the above (2), a long diameter of 20 mm was produced by a vacuum press forming machine FK-0531-D manufactured by Asano Laboratories.
A tray with a depth of 3 cm and an elliptical shape with a diameter of 15 cm and a minor axis of 15 cm is prepared.

(4) Judgment of odor 50 ml of distilled water is put into the tray obtained in the above (3).
Place another tray on top of it, cover it, heat it in a microwave oven (980W) for 3 minutes, boil the water, and then smell the odor of the lid by five different people and rank according to the following criteria. And the average of five persons is set as the odor determination value. 0: No odor. 1: There is very slight odor, but it is impossible to judge what odor it is. 2: A slight odor is felt, and determination of the type of odor can be attempted. 3: An unpleasant odor is clearly felt. 4: An unpleasant odor is strongly felt. 5: An unpleasant odor that cannot be put up is felt. (5) Thermal discoloration test From the sheet obtained in the above (2), a plurality of test pieces of 20 mm × 40 mm were cut out, placed on a rotating table in an electric oven at 220 ° C., and taken out at intervals of 10 minutes after 80 minutes, and discolored. Watch the time to start. (6) Cold resistance test 180 g of water was put into the tray obtained in the above (3), the upper portion was covered with a polyethylene film, heat-sealed and sealed, and then placed in a refrigerator at 5 ° C. for 4 hours and then taken out. The tray is dropped from a height of 60 cm and collides with a concrete plate surface to observe the state of breakage of the tray. If there is no damage after performing 5 pieces, ○, 1 to 3 pieces if cracks, 4 to
If there are five cracks, it is evaluated as x.

Examples 1 to 9 and Comparative Examples 1 to 4 Pellets, sheets and trays were prepared using the compounding agents shown in Tables 1 and 2. The obtained tray was subjected to odor judgment, thermal discoloration test and cold resistance test. The results are shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

The notes for Tables 1 and 2 are given below. * 1 S6008FD, high-density polyethylene manufactured by Showa Denko KK, melt flow rate 0.80 g / 10 min (JI
(SK 6760) * 2 SK711, ethylene-propylene block copolymer manufactured by Showa Denko KK, melt flow rate 0.75 g
/ 10 min (JIS K 6758) * 3 K7010, ethylene-produced by Chisso Petrochemical Co., Ltd.
Propylene block copolymer, melt flow rate
50 g / 10 min (JIS K 6758) * 4 Talc MS, talc manufactured by Nippon Talc Kogyo Co., Ltd. * 5 FR-89, titanium oxide manufactured by Furukawa Metal Mining Co., Ltd. * 6 Armostat 410, fatty amine manufactured by Lion Corporation , Antistatic agent * 7 Stabinex NT-Z1, zinc stearate manufactured by Mizusawa Chemical Co., Ltd. * 8 Kaowax EB, ethylene bisstearic acid amide manufactured by Kao Corporation * 9 ADK STAB AO-50, manufactured by Asahi Denka Co., Ltd. n-octadecyl-3- (3 ', 5'-ditertiarybutyl-4'-hydroxyphenyl) propionate * 10 Adecastab PEP-8, distearyl pentaerythritol diphosphite manufactured by Asahi Denka Co., Ltd. * 11 Mizcalizer DS, Zeolite manufactured by Mizusawa Chemical Co., Ltd. * 12 Mizukanite HP, Flypontite manufactured by Mizusawa Chemical Co., Ltd. Silica complex * 13 Alkamizer 1, Synthetic hydrotalcite manufactured by Kyowa Chemical Industry Co., Ltd., Mg ₄ Al ₂ (OH) ₁₂ CO _3.
12H ₂ O

Each of the trays obtained from the compositions of Examples 1 to 9 having the requirements of the present invention gave little odor even when heated, and gave sufficiently good heat discoloration resistance.
When a phosphorus-based antioxidant is used without using a phenol-based antioxidant, the odor due to heating tends to be slightly higher (comparison between Example 8 and Example 1). Compositions formulated with zinc stearate as a lubricant tend to have slightly more odor than when fatty acid amides are used. (Comparison between Example 9 and Example 4). Trays obtained from compositions with no adsorptive inorganics emit a pronounced unpleasant odor. Also,
Thermal discoloration easily occurs (Comparative Examples 1 to 3). When the amount of the adsorbable inorganic substance used is small, an unpleasant odor is clearly felt. In addition, thermal discoloration occurs quickly (Comparative Example 4). The cold resistance was all good within the range of the experiment, and no difference was observed.

[0023]

The use of the polyolefin composition of the present invention makes it possible to obtain a molded article suitable for food packaging containers, which generates less unpleasant odor under heating and has excellent heat discoloration resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // B65D 85/50 B65D 1/00 A

Claims (3)

[Claims] (A) 100 parts by weight of a polyolefin,
(B) 10 to 150 parts by weight of an inorganic filler and (C) at least one adsorbent inorganic substance selected from the group consisting of zeolite, frypontite-silica composite and hydrotalcite. Polyolefin composition. (A) 100 parts by weight of a polyolefin,
(B) 10 to 150 parts by weight of an inorganic filler, (C) 0.5 to 12 parts by weight of one or more adsorbable inorganic substances selected from the group consisting of zeolites, frypontite-silica composites and hydrotalcite, (D) 0.05 to 3 parts by weight of a phenolic antioxidant and (E) 0.05 to 3 parts by weight of a fatty acid amide
A polyolefin-based composition comprising 3.0 parts by weight. 3. A food packaging container obtained by molding the polyolefin composition according to claim 1 or 2.